1. Technical Field
The present invention relates to methods for making plated through holes. More particularly, the present invention relates to methods for making plated through holes usable to attach and support interconnection wires or probes.
2. Related Art
Plated through holes have been developed to connect electrical components on different layers of multiple layer semiconductor structures, such as layers of a printed circuit board (PCB). Plated through holes are further used to form interconnect elements enabling one PCB to be connected to components on a separate PCB or other discrete electrical components.
With a single multilayered PCB, the plated through holes formed in the PCB during manufacture serve to provide electrical coupling between circuits on the different layers. Fabrication of a PCB typically includes drilling a hole through a substrate made up of the layers, electrolytically plating the hole and conductive areas on the PCB layers with a metallic substance such as copper to form the plated through hole. A first circuit pattern is then formed in the conductive area on a first PCB layer and a second circuit pattern on a second PCB layer such that the plated through hole electrically couples the first circuit pattern to the second circuit pattern.
Plated through holes were developed for layered PCBs because it was generally found impractical due to the labor and cost involved to form multiple connections by physically inserting a conductive element (such as a wire) in a hole and then connecting the element to two circuits by soldering or other means. As described above, the usual method of forming plated through holes is to plate the circuits formed on the PCB layers and the through hole connections simultaneously so that the through hole connection is made as an integral part of circuit elements on different levels of the PCB without significant added labor or cost.
For two separate PCBs having electrical components to be connected after manufacture, or one PCB to be connected to a separate discrete electrical component, an insertable conductive element (such as a wire) forming a connector is still typically used. Such connectors can be formed by inserting connector pins into plated through holes of separate PCBs and soldering them in place. Such plated through holes provide connections between the pins and conductive regions on the separate PCBs or discrete components. An example of a technique of manufacturing PCBs with connector pins provided in plated through holes is described in U.S. Pat. No. 6,521,842, entitled “Hybrid Surface Mount And Pin Thru Hole Circuit Board.”
Recently PCBs have been used to support multiple resilient wires or probes to form probe cards used in temporarily connecting to electrical components, such as on semiconductor wafers for testing. It would be desirable to provide a method for efficiently manufacturing such multiple temporary connection elements for probe cards.